A hydrogen-oxygen fuel cell is an apparatus which converts the energy of the chemical reactions between a fuel and an oxidant directly into low voltage, direct current electricity. Typical hydrogen-oxygen fuel cells are comprised of an electrolyte chamber which contains an electrolyte, and a cathode and an anode which are positioned in a spaced-apart relationship from each other in the electrolyte. The cathode and anode are made of a catalytic material which causes the fuel and the oxidant to react at a sufficiently high rate of reaction to produce useful amounts of electrical power.
In operation, a fuel is fed to the anode where it is oxidized in the electrolyte at the catalytic surface of the anode causing the liberation of electrons. Simultaneously, an oxidant is fed to the cathode where it is reduced in the electrolyte at the catalytic surface of the cathode causing consumption of electrons. The electrons generated at the anode are conducted to the cathode through a conductor which is attached to the cathode and anode. The transfer of electrons from the anode to the cathode causes an electrical current to flow which can be used to operate electrical devices.
The oxidant which is used in the operation of a hydrogen-oxygen fuel cell can be pure oxygen but more typically is an inexpensive, readily-available, oxygen-containing gas such as air.
The fuel used in the operation of hydrogen-oxygen fuel cells can be pure hydrogen but more typically is a material which can be reduced to provide hydrogen. Fuels other than hydrogen which are commonly employed include hydrazine (N.sub.2 H.sub.4) and organic compounds such as formaldehyde, ethanol, methanol, propylene, methane and the like.
Hydrogen-oxygen fuel cells have many inherent advantages over other types of apparatus used to produce electricity. The manufacturing cost of hydrogen-oxygen fuel cells is quite low and there are no mechanically moving parts. Hydrogen-oxygen fuel cells are noiseless, clean and the by-products are unobjectionable. Hydrogen-oxygen fuel cells consume fuel only when power is drawn from the system. After the electrical power is drawn off, the cell can be rejuvenated by simply adding additional fuel and oxidant.
The production of electricity using a hydrogen-oxygen fuel cell as described above is well known in the art. Much research work has been conducted to overcome certain problems encountered with hydrogen-oxygen fuel cells with, at best, limited success. Recently, the research work on hydrogen-oxygen fuel cells has intensified because of use of hydrogen-oxygen fuel cells on space vehicles. In normal operation, space vehicles rely on solar cells to produce required electrical power. However, when the solar cells are shielded from the sun, a backup power source must be used to provide the required electrical power. Because of their simplicity of construction and operation, hydrogen-oxygen fuel cells are considered to be an ideal alternate source of electrical power for space vehicles.
Certain problems have, however, been encountered. One such problem is that the amount of electrical power produced is relatively low and can only be produced for a relatively short period of time. A still further problem is that as the hydrogen-oxygen fuel cells are operated, certain by-products are produced as a result of the chemical reactions which occur. The principal by-products are water and carbonates. The by-product water rapidly dilutes the electrolyte which increases the internal resistance of the hydrogen-oxygen fuel cell and reduces the rate of chemical reaction such that the amount of useful electrical power which is produced in a given time period is substantially reduced. When the electrolyte becomes excessively diluted or contaminated with carbonates, it is necessary to discard the diluted and/or contaminated electrolyte and refill the hydrogen-oxygen fuel cell with fresh concentrated electrolyte.
What would be highly desirable would be a hydrogen-oxygen fuel cell and a method for operating the hydrogen-oxygen fuel cell which would allow the generation of larger amounts of electrical power for longer periods of time and which would not require frequent changes of electroyte in the hydrogen-oxygen fuel cell in order to maintain satisfactory performance.